Breast cancer is the most commonly diagnosed cancer among women and the second leading cause of cancer death among females. In 2007 there will be well over 200,000 new cases of breast cancer diagnosed in the United States and approximately 40,000 women will die from metastatic breast cancer. Mammography screening has had a major impact on the rate of death. From 1950 to 1990, the death rate from breast cancer had been unchanged. In 1990, the death rate suddenly began to fall in direct relationship to the onset of widespread mammography screening that began, based on national statistics, in the mid-1980's. The death rate has decreased by 25% since 1990, and national and international data suggest that this decrease is predominantly due to early detection from screening.
A decrease in deaths of 25% is a major achievement but clearly not a complete solution to the problem. Mammography still does not find all cancers and does not find all cancers early enough to save all women. More specifically, many breast cancers have essentially the same or very similar x-ray attenuation as normal fibroglandular tissue and, as a consequence, can remain hidden on standard x-ray mammography in both digital and film/screen approaches.
Conventional x-ray imaging, as used in mammography and other applications, relies on differences in the absorption of x-rays, e.g., in bones versus soft tissue. Whether measured with film or with film-less digital methods, the fundamental limitations of absorption radiography remain with respect to tradeoffs between contrast and dose.